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C#/.net图片压缩算法
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

/// <summary>
/// 图片压缩
/// </summary>
public class ImageCompress
{
/// <summary>
/// 指定缩放类型
/// </summary>
public enum ImageCompressType
{
//***指定高宽缩放(可能变形)
WH = 0,
//***指定宽,高按比例
W = 1,
//***指定高,宽按比例
H = 2,
//***指定高宽裁减(不变形)
Cut = 3,
//***不指定,使用原始
N = 4
}

#region Compress
/// <summary>
/// 无损压缩图片
/// </summary>
/// <param name="sFile">原图片</param>
/// <param name="dFile">压缩后保存位置</param>
/// <param name="height">高度</param>
/// <param name="width"></param>
/// <param name="flag">压缩质量 1-100</param>
/// <param name="type">压缩缩放类型</param>
/// <returns></returns>
public bool Compress(string sFile, string dFile, int height, int width, int flag, ImageCompressType type)
{
System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
ImageFormat tFormat = iSource.RawFormat;

//****缩放后的宽度和高度
int towidth = width;
int toheight = height;

int x = 0;
int y = 0;
int ow = iSource.Width;
int oh = iSource.Height;

switch (type)
{
case ImageCompressType.N://***原始高宽
{
towidth = ow;
toheight = oh;
break;
}
case ImageCompressType.WH://指定高宽缩放(可能变形)
{
break;
}
case ImageCompressType.W://指定宽,高按比例
{
toheight = iSource.Height * width / iSource.Width;
break;
}
case ImageCompressType.H://指定高,宽按比例
{
towidth = iSource.Width * height / iSource.Height;
break;
}
case ImageCompressType.Cut://指定高宽裁减(不变形)
{
if ((double)iSource.Width / (double)iSource.Height > (double)towidth / (double)toheight)
{
oh = iSource.Height;
ow = iSource.Height * towidth / toheight;
y = 0;
x = (iSource.Width - ow) / 2;
}
else
{
ow = iSource.Width;
oh = iSource.Width * height / towidth;
x = 0;
y = (iSource.Height - oh) / 2;
}
break;
}
default:
break;
}

Bitmap ob = new Bitmap(towidth, toheight);
Graphics g = Graphics.FromImage(ob);
g.Clear(System.Drawing.Color.WhiteSmoke);
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.HighQuality;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(iSource
, new Rectangle(x, y, towidth, toheight)
, new Rectangle(0, 0, iSource.Width, iSource.Height)
, GraphicsUnit.Pixel);
g.Dispose();
//以下代码为保存图片时,设置压缩质量
EncoderParameters ep = new EncoderParameters();
long[] qy = new long[1];
qy[0] = flag;//设置压缩的比例1-100
EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
ep.Param[0] = eParam;
try
{
ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo jpegICIinfo = null;
for (int i = 0; i < arrayICI.Length; i++)
{
if (arrayICI[i].FormatDescription.Equals("JPEG"))
{
jpegICIinfo = arrayICI[i];
break;
}
}
if (jpegICIinfo != null)
{
ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
}
else
{
ob.Save(dFile, tFormat);
}
return true;
}
catch
{
return false;
}
finally
{
iSource.Dispose();

ob.Dispose();

}
}
#endregion
}

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本文作者:Bruce
本文地址:C#/.net图片压缩算法 | 数据库之家